IAH is easier than EWR for international-to-domestic transfer. I'll do it with less 90 minutes if the following requirements are met:

- Carry-on only
- Not late afternoon, especially in the summer (thunderstorms)
- Traveling by myself, or with other equally-savvy travelers
- Other, later flights to take to my destinations should I miss my connection

If any of those conditions don't fit your travel, err on the side closer to 2 hours. A visit to the E P-Club is fine consolation if you blitz through formalities.

Regarding your travel at EWR (I've never actually connected there, being EWR-based), I can definitely see how several unrelated delays can pare your 'long' layover down to a real hustle. That's just the way it goes over there. 3 hours is the magic number in my mind for any connection at EWR that involves an international flight.